A RECONNAISSANCE SURVEY OF PUMICE SOILS.

New Zealand Journal of Agriculture, Volume XXX, Issue 1, 20 January 1925, Page 1

A RECONNAISSANCE SURVEY OF PUMICE SOILS.

ROTORUA COUNTY. ( Continued.)

B. C. ASTON, F.I.C.

, F.N.Z.Inst., Chemist to the Department.

/. III. KAHAROA AND TE PU. IN the November and December ,numbers of the Journal it has been • shown that the great extent of both Mamaku and Rotorua Basin lands are either sandy loams or sandy silts. The latter occupy by far the greater area. As one travels north from Lake Rotorua the soil becomes even coarser. This increase in coarseness is due to the larger amount of fine gravel present. A new name is therefore required to designate this type of soil, which should be known as the “ Kaharoa fine gravelly sand.” It will be seen on comparing the results of analyses that the “ fine gravel ” fraction, from being almost a negligible quantity in the pumice soils previously described, is now present in quantity ranging from one-fifth to one-quarter by weight of the soil ; and when to this is added the stones and gravel which are separated from the soil in preparing it for analysis the coarseness is further increased from another most appreciable cause. Concurrently with the increase in the coarser particles the proportion of the finer particles is necessarily decreased.- This extreme coarseness of the soil is noticeable on leaving Hamurana and climbing the slopes of the natural rampart leading to the terrace on the northern slope near the top,- above, but facing away from, Rotorua Lake, in scrub land, at 625 ft.,

and in the tawa-rimu-mangeao forest beyond and below this terrace ■land. Has this terrace land ever borne any primitive vegetation larger than scrub which has been removed by the aboriginal owners, or is it that the water content of the soil has not been sufficient for the development of forest ? In the forest below, the soil is moister and the trees unusually tall. There is no difference in the mechanical or chemical composition of the soil, save possibly the water content, and this may be the factor which has determined the quality.of the natural vegetation, the water draining - out . readily from the high terracea large catchment —on to the lower, slopes now densely forested. A similar condition of things. exists on the area known as the Kapakapa Road, 400 ft. above Rotorua. This road runs along a high slope north of the latter site. The soil is similar.to sample R 976, and bush sickness is more - prevalent here, the stock having to be changed perhaps oftener than in any other part. At the end of the road, which falls to about 150 ft. above Rotorua, there is some fine land which is much moister and bn which the sickness is never experienced. This carries very tall forest similar to that on R 976. Springs are in evidence in many places in the lower area, but are entirely absent . on the higher portions of the slope. - A similar instance is found on the Kaharoa Road, a forested area ; where there are no springs the trouble appears, but where there is plenty of spring or creek water the stock are said to be perfectly healthy. Thus at the extremity and lower portion of these two blind roads the cattle-sickness is unknown. The writer considers this as being a ' parallel to the ' well-known case of the lake-side paddocks (see p. 370, December, 1924, Journal) and the bush-sick areas up on the hills. Where the soil is kept well saturated with water by seepage from springs or surface water there is no sickness, and where the soil is dependent on rainfall the soil-water so soon drains away that there is not sufficient to act as a carrier- of mineral plant-food from the soil to the plant-roots. , An analogous case occurred once in the Norsewood district (Hawke’s Bay). Here cows suffered in a droughty. season from bone malnutrition, although there was chemical evidence that phosphates were not deficient in the soil. The water was probably the limiting factor, the natural pasture being insufficiently nutritious to keep the stock healthy, In the chemical analyses of these fine gravelly sands there is little to distinguish them from the Rotorua Basin soils save a slightly higher lime content and a slightly lower available iron content. Available and total phosphoric acid, as . in all pumice soils, is deficient. On traversing the Kapakapa, Kaharoa, and the . main RotoruaTauranga roads in the vicinity of Te Pu the extreme coarseness of the soil is readily discernible to the traveller in the road cuttings. One may, with the aid of mechanical analyses, unhesitatingly affirm that a large extent of country at the north end of the lake is marked by such a coarseness of . texture that the student of soil science would be put on his guard and naturally look for untoward results in farming such country; but where the physiography of the-country is such that the surface soil is supplied with the optimum. requirement of - water he would come to lands which unite in the highest degree two essential conditions of fertilityporosity and a constant supply of water.

There is a strong local opinion that the stock by drinking springwater are thereby cured of bush sickness, or if pastured in the vicinity of springs or creeks never become bush sick; whereas if the drinkingwater for. stock is supplied from rain-water caught and stored in concrete tanks or cisterns the animals suffer from iron-hunger. Analyses of the waters from springs and tanks, however, afford no evidence to support the truth of this local belief. The explanation of the immunity from iron-starvation which stock enjoy in country which is well watered with springs is probably that in such areas the soil is well supplied with moisture from the high land. The greater moisture content of the soil enables the pasture to absorb larger amounts of plantfood, especially iron, from the soil around it. Such immune areas are not more than 100 ft. to 350 ft. above lake-level, but the worst country is some 400 ft. to 600 ft. above the lake and contains no running water or signs of springs. An instance was given to the writer by the manager for a very well known landowner who has interests in this area of a mob of 1,000 sheep from Hawke's Bay which were kept here from the end of January until August. Those pastured on country with springs went ahead, but those pastured on adjacent land containing no springs and supplied only with tank-water did not improve in condition. When, however, they were transferred to land with springs they' improved like the others. The obvious treatment which these facts demonstrate as fitting for the farmer to practise on such country is to fence off the area showing unusual moisture in the soil, and to endeavour to enhance to a greater degree the superior fertility which it shows over the drier country by applying the best top-dressing that can be procured. The one that has been found most effective at the Mamaku Demonstration Farm is a mixture of superphosphate and basic slag of high grade. This mixture is a fertilizer containing all the mineral plant-foods which bushsick country needs —iron, phosphates, calcium in non-caustic form, and sulphuras well as such elements as manganese. Potash, it should be noted, is present in all pumice soils in comparative abundance. The climate of the Kaharoa area is possibly much, milder than that of Mamaku and even that of Rotorua, for the forest contains two trees, the mangeao and kohekohe, which indicate 'milder conditions. The forest, which is of the tawa-rimu type, is ■ exceptionally tall, that at the end of the Kaharoa Road consisting as follows : — Forest trees : Beilschmiedia tawa, Dacrydium cupressinum (rimu), Knightia excelsa (rewarewa), Laurelia novae-zelandiae (pukatea), Litsaea calicaris (mangeao), Podocarpus ferruginous (miro). Shrubs and small trees : Aristotelia racemosa (wineberry), Caryodetus serratus, Dysoxylum spectabile (kohekohe), Fuchsia excorticata, Geniostoma ligustifolium, Hedycarya arborea (porokaiwhiria), Melicytus ramiflorus (mahoe), M etrosiderog florida, M. robusta (rata), M. scandens, Piper excelsum (kawakawa), Rhipogonum scandens (supplejack), Rubus australis (lawyer), Weinmannia racemosa (tawhero). Forest-floor plants : Alseudsmia macrophylla, Aspidium hispidum, Asplenium bulbiferum, Astelia Solandri, Cyathea dealbata, Hymenophyllum sp., Lomaria discolor, L. capense, L. filiformis, Lygodium articulatum, Muehlenbeckia australis, Polypodium pennigerum, P. punctatum, P. serpens, Pteris scaberula, Uncinia sp. '

The illustrations show the' texture of the ■ three • main types of pumice soils described in the last three numbers of the Journal together with a Wellington ■soil for comparisonwhen treated in the following manner and - allowed to dry and then photographed : -2 c.c. of fine earth are mixed with 3 c.c. of water in a 10 c.c. glass cylinder, and after light rubbing with a rubber-tipped stirring-rod are ■shaken for four minutes. ' A 15 cm. filter-paper is moistened with 3 c.c. of water .and spread flat on a horizontal plate of glass. The cylinder of soil and water, ■closed by the thumb, is inverted -1 cm. above the centre of the paper, and the contents are rapidly released. The extent to which the soil becomes spread over the paper is seen to vary with the fineness— as the soil becomes increasingly finer the larger is the area covered ; conversely, the coarser the soil the smaller is the space occupied. The Wellington loam (R 814) shows what a good fertile soil looks like. The.Oturoa sandy loam (K 1138) closely resembles the first, but is slightly coarser ; the Mamaku sandy silt (R 182) is obviously a very coarse-grained ■soil; while the Kaharoa fine gravelly sand (R 1117) is the extreme type of coarse pumice soils. The disk partly shown in each illustration represents the 15 cm. filter-paper (about 6 in. diameter), and thus gives the reduced scale.

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A good deal of the country about here has been tutu and fern'land, and possibly represents. old Maori clearings. ■ . In spite of the great coarseness of these Kaharoa and Te Pu soils there are mitigating circumstances which improve the prospects of the settler on these lands and reconcile him to his lot. One would think that the.climate is warmer and the land more sheltered from winds than are most pumice lands, but the great factor in combating adverse soil conditions must be the proximity of land free from bush sickness and suitable for change paddocks. One other factor is. the freedom from the counter-attraction of more remunerative forms of industry. There is no sawmilling trade or tourist traffic to absorb the energies of the settlers, and consequently the community is purely a farming one ; the interests of all are identical. The visitor is impressed with the fine type of settlers and the way they are combining for the common good ; so that even on the worst class of country— soil of which is so coarse and dry that the stock have to be changed twice a year there is a healthy optimistic tone about the district which is most cheering and helpful to the investigator of a difficult problem.

Laboratory Description of Soil. (Classification of United States Department of Agriculture, modified.) Analysis of “ Fine Earth ” passing 2 mm. Sieve. Ston“s and Gravel. Remarks Fine Gravel. Coarse Sand. Fine Sand. Silt. Fine Silt. Clay. Moisture. Loss on Ignition. No. Coarsest Pumice Lands. Description of Soil. (Classification, of United States Department of Agriculture, modified.) Fine Gravel. Analysis of “ Fine Earth ” passing 2 mm. Sieve. Ston-s and Gravel. Remarks Coarse Sand. Fine Sand. Silt. Fine Silt. Clay. Moisture. Loss on Ignition. R Fine gravelly sand 26-0 38-3 II’I 8-6 Coarses 3’9 t Pumic • 1’2 e Lands. r-6 8-4 8-6 ' Pasture, Kaharoa Road ; 200 ft. above Lake Rotorua. 1105 1108 20'6 46-r 9-0 6-9 5’0 i-i i'5 1'0-3 7’2 Pasture, Glenmore, Kaharoa Road 130 ft. above Lake Fine gravelly sand 26-0 38-3 II-I 8-6 3'9 • 1*2 i-6 8-4 8-6 Pasture, Kaharoa Road ; 200 ft. above Lake Rotorua. 1108 1114 20-6 46-1 9-o 6-9 5-o I-I i-5 io-3 7'2 Pasture, Glenmore, Kaharoa Road 130 ft. above Lake Rotorua. Coarse sand 13'7 52-6 11’2 8-6 4’7 1’3 I’O 6:7 5-i Rotorua. Pasture, Kaharoa Road. ' 1114 1117 sand Fine gravelly 13-7 20-3 52-6 44’0 II-2 ii-8 8-6 9’9 4'7 3'6 1'3 1’2 1-0 i-3 6-7 7-5 5-i 3-1 Pasture, Road. Pasture, Road 400 ; 1117 II2I Fine gravelly • » 20'3 17’9 44’0 52-r n-8 9’3 9’9 7’8 3'6 4’4 1-2 o-6 . 1’3 I-I 7-5 6-4-3'1 5’1 Pasture, Road ; Pastune, ft. ; II2I 1134 » Coarse ... 17'9 ri-9 52-i 48-4, 9’3 13-7 7-8 9.7 4-4 5’4 o-6 i-4 I-I r-9 6-4 7.7 5-i 13-0 ft. ; Kapakapa fern Lake ft. ; 1134 1136 2'9 55’4 15-5 10-7 6-4 1'9 o-9 6-5 3-i ' Pasture, flat-topped ridge, Lake Rotoiti; .100 ft. Coarse sand n-9 48-4 13’7 9’7 5’4 1-4 r-9 7.7 13-0 Lake Rotoiti, fern slopes ; 105 ft. 1136 1143 >> sand gravelly 2-9 23-7'. 55’4 39’0 15'5 io-7 10-7 8-2 6-4 7.7 i-9 o-8 0-9 ’ 1’2 6-5 8-6 3’1 5-o Pasture, flat-topped ft. Mahgarewa-Kaharoa Forest, little ; 1143 1145 sand gravelly » 23’7 19-6 39-o 33-o 10-7 13-2 8-2 12’3 7’7 7-r o-8 2-2 1-2 2-4 8-6 ro-6 5-o i5-.o Forest, little ; Te - Road. land, 1145 973 » » 19-6 26-9 33'0 33-7 13-2 13-5 12-3 8-9 7-i 4’7' 2'2 o-8 2-4 2-4 ro-6 8-o 15-0 15-4' Fern - land, Scrub land; 625 973 976 » ■ » 26-9 19-8 33’7 38-8 13'5 14-9 8-9 .8-4 4’7' 5’3 0-8 o-8 2-4 I’O 8-o 9-r 15’4 13'6 land; Lake 625 Forest, rimu-tawa-mangeao. 976 970 » » 19-8 21’2 38-8 32-7 14’9 15’9 8’4 9-9 5-3 4'9 o-8 o-i 1-0 i-7 • 13-6 Forest, rimu-tawa-mangeao. ir-9 I 9’° Fern and scrub regrowth, Hamurana ; 300 ft. above lake. 970 S 61 » sand 21*2 12’6 32-7 32-0 15'9 12-5 9’9 9'3 4'9 4-6 o-i r-7 r-7 23’3 ii’9 Pasture, Rotorua Lake side ;. probably floated beach. 19-0 Fern and scrub regrowth, Hamurana ; 300 ft. above lake. S H 480 Fine gravelly sand 16-8 45-6 17’9 8-3 2-3 1’2 3’5 4-r 20-0 Pasture, Rotorua Lake side ; probably floated beach. 61 482 17-6 4i-7 J 12-8 15-0 3’5 1’2 1-3 6-8 24-r Waerenga East. Coarse sand 12*6 32-0 12'5 9'3 4-6 i-7 23’3 V 5’7 Pasture, Rotorua Lake side ; probably floated beach. H 480 Fine gravelly sand i6-8 45'6 17-9 8-3 2-3 1’2 3’5 4-1 20-0 Pasture, Rotorua Lake side ; probably floated beach. 482 -1 17-6 41-7 12-8 15-0 3'5 1’2 1-3 6-8 24-1 Waerenga East.

TABLE 5. MECHANICAL ANALYSES. (Results, except R 970, are percentages on air-dried soil.)

Laboratory Volatile Matter. i-per-cent. Citric-acid Extract, Dyer’s Method ; Hall’s Modification (“ Available ” Plant-food). Hydrochloric-acid Extract (“ Total ” Plant-food). Hydrogenion Determination. Fe (Iron) No. Locality. * On Airdrying. * At too’ C. On ! Ignition. Tota Nitrog Lime, CaO. Magnesia, MgO. Potash, K 2 O. Phosphoric Acid, P2O5. Lime, CaO. Magnesia, MgO. Potash, K 2 O. Phosphoric Acid, P2O5. pH Value. Extracted by 1-per-cent. Citric Acid ■ Volatile Matter. Total < Nitrogen. r-per-cent. Citric-acid Extract, Dyer’s Method ; Hall’s Modification (“ Available ” Plant-food). Hydrochloric-acid Extract (“ Total ” Plant-food). Hydrogenion Determination. Fe (Iron) Extracted by 1-per-cent. Citric Acid * On Airdrying. * At 100’ c. On Ignition. Lime, CaO. Magnesia, MgO. Potash, k 2 o. Phosphoric Acid, p 2 o 5 . Lime, CaO. Magnesia, MgO. ■ I Potash, k 2 o. Phosphoric Acid, P2O5. pH Value. Coarsest Pumice Lands.' R 'nos Rotoiti S.D., Block 5, Section 2 13 i-74 7'97 0-225 0-289 0-042 0-031 o-oio 0-35 0-16 0-02 0-032 1105 1108 Rotoiti Block Section 5, Glenmore, ft. .. 130 13 29 - i-74 1-82 7'97 10-28 Courses 0-294 0-156 0-060 0-020 0-006 0-71 0-31 0-13 0-02 0-032 0-225 t Pumice 0-289 Lands. 0-042 0-031 o-oio o-35 0-16 0-09 0-02 0-032 1108 1114 Glenmore, ft. 130 .Rotoiti Block Section 7 29 15 1-82 ’00 I 10-28 6-42 0-294 0-192 0-156 0-109 0-060 0-041 0-020 0-016 0-006 0-004 0-71 0-40 0-31 0-22 0-13 O-II 0-02 0-02‘ 0-032 0-037 1114 1117 Rotoiti Block Section 7 Kapakapa Road, ft. ... 15 18 Ii-68 6-42 7-63 0-192 0-208 0-109 0-161 0-041 0-026 0-016 0-016 0-004 0-006 0-40 0-31 0-22 0-16 o-ii 0-1'5 0-02 0-04 0-037 0-036 1117 II2I . Kapakapa Road, ft. 410 Kapakapa Road, . 18 13 r-68 r-o6 7-63 6-71 0-208 0-235 o-i6r 0-448 0-026 0-036 0-016 0-015 0-006 O-OII 0-31 o-66 , o-i6 0-23 0-15 0-09 0-04 0-04 0-036 0-037 II2I 1134 Kapakapa Road, ft., Rotoiti, ft. . 105 13 18 1-06 1-96 6-71 7’94 0-235 0’211 0-448 0-139 0-036 0-031 0-015 0-016 o-oii 0-006 o-66 o-86 0-23 0-29 0-09 0-12 0-04 0-03 0-037 0-023 1134 1136 Rotoiti, ft. 105 Rotoiti, ft., flat-topped 18 14 1-96 1-18 7-94 6-39 O-2II 0-208 0-139 0-307 0-031 0-016' 0-016 0-024 0-006 0-008 o-86 -43 0-29 o-53 0-12 0-16 0-03 0-03 0-023 0-040 1136 1143 Rotoiti, ft., flat-topped ridge Mangarewa Gorge, 445 14 23 i-i8 i-6o 6'39 -9’03 0-208 0-222 0-307 0-172 0-016 0-026 0-024 0-020 0-008 0-004 i-43 0-46 o-53 o-io p-i6 ' 0-05 0-03 0-02' 0-040 5’5 0-017 1143 1145 Mangarewa Gorge, 445 Kaharoa, ft. . 365 23 23 i-6o 2-60 9'03 -00 1 0-222 0-221 0-172 6-089 0-026 0-026 0-020 0-026 0-004 0-004 0-46 0-22 O-IO 0-17 0-05 0-08 0-02 0-03 0-036 5-5 0-017 1145 973 Kaharoa, ft. 365 Rotoiti, scrub . 23 13 2-60 2-44 1’00 8-17 0-221 O-23O 0-089 0-109 0-026 0-020 0-026 0-018 0-004 0-004 0’2.2 0-32 0-17 0-22 o-o8 0-09 0-03 0-04 0-036 0-018 973 976 Rotoiti, scrub Rotoiti, forest 13 ' 29 2-44 1’00 8-17 8-44 O-23O 0-255 . 0-109 ’ O-I43 0-020 0-033 0-018 0-019 0-004 0-002' 0-32 o-47 0-22 0-20 0-09 0-08 0-04 0-03 o-ox8 0-028 976 97o Rotoiti, forest Hamurana, ft. .. . 29 28 00 1-70’ 8-44 12-06 0-255 0-224 O-I43 0-125 0-033 0-058 0-019 0-023 0-002 0-005 0-47 o-45 0-20 0-23 0-08 0-08 0-03 0-06 0'028 0-020 97o S 61 Hamurana, ft. . 300 Lake-side, . . ■ 23-32 7-40 0-197 6-1’50: 0-022 O-OII 0-006 0-32 0-12 0-07 0-04 0-023 28 1-70 12-06 0-224 0-125 0-058 0-023 0-005 o-45 0-23 0-08 0-06 0-020 S 61 Lake-side, Rotorua .. 23-32 7'40 0-197 0-150 0'022 O-OII 0-006 0-32 0-12 0-07 0-04 0-023

TABLE 6. CHEMICAL ANALYSES. (Results, except *, are percentages on soil dried at 100° C.)